DESCRIPTION OF THE PRIOR ART
Present commercial zig-zag picket heating elements are provided in the form of a one-piece cylindrical shell, which surrounds the crucible holding the material to be critically heated. Such heaters are conventionally machined from graphite to function as an electrical resistance heater which produces the relatively high temperatures required, for example, in crystal growing operations. Because such heaters are very expensive, and quite brittle and subject to cracking or chipping while in use, which affects the uniformity of their application of heat to the crucible, the need for the frequent replacement of such heaters has added considerably to the expense of the crystal growing operation. Some of the following patents cited in the afore-mentioned applications are indicative of the present state of the art.